The present invention relates to a technology that enables high availability of a client-server system at the time of overload, by priority control processing.
In recent years, client-server systems using Web services have begun to be constructed for use in business transactions between companies that require high availability.
The web service is a new form of application system: by connecting a server to clients of separately-constructed different systems, the web service is constructed. In other order placement and acceptance systems in companies except for the system built as the web service, for example, due to a difference in the communication protocol or the notational method for the contents of communication, dynamic connection to a new trading partner could not be established, so that order placement and acceptance operations could not be automated. The web service solves the problem described above: the web service does not define the type of a communication procedure (which will be hereinafter referred to as a protocol type) at the protocol layer 4 between the server and each of the clients connected through the TCP/IP network, assumes and permits use of a plurality of protocols such as use of both of the HTTP protocol and the SMTP protocol, shares the format for the contents of communication in the XML (extensible Markup Language), and releases the notational method on the Internet, thereby ensuring dynamic connectivity among different systems.
On the other hand, in conventional client-server systems, there is known a technology for installing a priority control device between the server and the clients. This technology is disclosed in U.S. Pat. No. 6,415,313, for example. By installing the priority control device, even at the time of server overload, the server can respond to a request from an important client. The request from a client will be referred to as a request message. The priority control device prioritizes request messages from clients, causes the request messages with lower priorities to be waited for transmission, and relays the request messages to the server sequentially in the order of the priorities of the request messages.